Article 23: Progressing Cavity Pumps for Wastewater Treatment Plants

By

Scott Champlin

President

Pumping Solutions, Inc.

Chicago, IL

 

Progressive cavity (PC) pumps are self-priming rotary positive displacement pumps with smooth output flow.They are capable of pumping both thick and thin fluids, and do very well at pumping liquids with high solids and abrasive content.These capabilities have made the progressive cavity pump THE pump of choice for many applications in the wastewater treatment industry.†††

 

In recent years, advances in pump design, electronic monitoring, and materials of construction have allowed the PC pump to handle more severe application conditions, while at the same time improving the pumpís energy efficiency and decreasing maintenance requirements.

 

The purpose of this article is to give a basic overview of the pumps operating principle and review some of the new technical innovations that end users might be able to benefit from.

 

Rene Moineau invented the progressive cavity pump in France in the 1930ís.†† The pumping element is made from the rotor and stator elements.Normally the rotor is made of steel and is the shape of a single helix external shape, the stator is normally made from an elastomer and is the shape of a double helix internal shape.The rotor is manufactured to be slightly larger in size than the stator so that there is an interference fit when the rotor is inserted into the stator.As the rotor turns inside the stator, a cavity is formed between the two shapes and progresses axially from one end of the element to the other.

 

 

 

 

 

 


The PC pump is made of three major sections:

 

 

 

 

 

 

 

 

 


A) The pumping element†††††††††††††††††††† B) The suction housing††††††††††† C) The drive train

(Courtesy Allweiler Pump, Colfax group)

In recent years many improvements have been made in these three areas to improve the pumps overall performance.

 


Improvements in drive train design:

 

 

 

 

 

 

 

 

 

 


Features

Benefits

Close coupled or Block Design††††††††

Smaller pump package

Less Upfront Cost

No drive alignment issues

Eliminates the need for safety guards

Easy Access to mechanical Seal

Simplifies seal service, reduces down time

Sealed Pivot Style Universal Joints

Fewer parts

Long lasting and easy to work on

Protects Drive-shaft, Coupling Rod and Rotor from damage.

Augers Feed Screw / Coupling Rods

Better NPSHR values

Higher Volumetric efficiencies

Higher % Solids capabilities

 

 

Improvements in Suction Housings:

 

 

 

 

 

 

 

 

 

 

 


Features

Benefits

Oversized Open Hopper Inlets

Handle thicker liquids

Special Compression Zones

Increased volumetric efficiency

Oversized Hopper With Double Auger

Eliminates bridging

Handles filter cake up to 55% solids

 

 

Improvements in Pumping Element:

 

 

 

 

 

 

 

 


 


Features

Benefits

New 2 x 3 rotor/stator geometry

Increased flow per revolution and reduces initial pump cost.

Equal Wall Stators

Doubles pressure capability per stage

Tie Rod Construction

Easy stator change out with standard socket set

Hollow Cast Rotors

Increase rotor and stator service life

Temperature Probe

Protects against dry run

Ductile Coated Chrome Rotors

Extend wear life of rotor

Does not flake off like standard chrome coatings

 

About the Author

Scott Champlin is a President of Pumping Solutions, Inc., a pump distributor based in Chicago area, and offering a variety of services in pumps and systems applications. He can be reached via web site www.pump.ws

 

Let us know if you may have any questions. We would be glad to help. E-Mail your questions to:

 

DrPump@Pump-Magazine.com

 

Back to PUMP MAGAZINE Page

 

ARTICLES LIST